Dominica Sanctissime Trinitatis: "Teach all nations"

Matt 28:18-20
At that time, Jesus said unto His disciples: All power is given unto Me in heaven and in earth. Go ye, therefore, and teach all nations, baptizing them in the Name of the Father, and of the Son, and of the Holy Ghost. And so on.

Homily by St. Gregory of Nazianzus, Patriarch of Constantinople.
Treatise on the Faith.
There is no Catholic but knoweth that the Father is a Very Father, the Son a Very Son, and the Holy Ghost a Very Holy Ghost, even as the Lord Himself saith unto His Apostles: "Go ye and baptize all nations in the Name of the Father, and of the Son, and of the Holy Ghost." This is that Perfect Trinity Who is but One being, and of Whom therefore we testify that His Substance is one. For we make no division in God, as divisions are made in bodies, but we testify, that, according to the power of the Divine Nature, Which standeth not in matter, the Persons named have a real existence, and that God is One.

Dominica post Ascensionem: "He is with us alway even unto the end of the world"

John 15:26-27; 16:1-4
At that time, Jesus said unto His disciples: When the Comforter is come, Whom I will send unto you from the Father, even the Spirit of truth, Which proceedeth from the Father, He shall testify of Me. And so on.

Homily by St. Augustine, Bishop of Hippo.
Tract 92 John.
The Lord Jesus, in that discourse which He addressed to His disciples after the Last Supper, when He was on the very eve of the Passion, when He was, as it were, about to go away and leave them as touching His bodily Presence, albeit as touching His spiritual Presence, He is with us alway even unto the end of the world, Matth. xxviii. 20, in that discourse He exhorted them to bear patiently the persecution of wicked men, of whom He speaketh as "the world", out of which world, nevertheless, He saith that He hath chosen even His disciples themselves, xv. 19, that they might know that it was by the grace of God that they were what they were, 1 Cor. xv. 10, whereas it was by their own sins that they had been what they had been.

Ascension: "the disciples' slowness to believe that the Lord had indeed risen from the dead, was not so much their weakness as our strength"

From the Holy Gospel according to Mark
Mark 16:14-20
At that time, Jesus appeared unto the eleven disciples as they sat at meat, and upbraided them with their unbelief and hardness of heart, because they believed not them which had seen Him after He was risen. And so on.

Homily by Pope St. Gregory the Great
29th on the Gospels
I may be allowed to say that the disciples' slowness to believe that the Lord had indeed risen from the dead, was not so much their weakness as our strength. In consequence of their doubts, the fact of the Resurrection was demonstrated by many infallible proofs. These proofs we read and acknowledge. What then assureth our faith, if not their doubt? For my part, I put my trust in Thomas, who doubted long, much more than in Mary Magdalene, who believed at once. Through his doubting, he came actually to handle the holes of the Wounds, and thereby closed up any wound of doubt in our hearts.

Now confirm to our minds the trustworthiness of the fact that our Lord did indeed rise again from the dead, it is well for us to remark one of the statements of Luke Acts i. 4. "Eating together with them, He commanded them that they should not 1 John xiv. 16, 17 xvi. 7. depart from Jerusalem and a little afterward: "While they beheld, He was taken up, and a cloud received Him out of their sight." Consider these words, note well these mysteries. After "eating together with them He was taken up." He ate and ascended: that the fact of His eating might show the reality of the Body in Which He went up. But Mark telleth us that before the Lord ascended into heaven, He upbraided His disciples; with their unbelief and hardness of heart. From this I know not why we should gather, but that the Lord then upbraided His disciples, for whom He was about to be parted in the body, to the end that the words which He spoke unto them as He left them might be the deeper imprinted on their hearts.

Dominica V post Pascha: "whatsoever is asked, which tendeth not to salvation, is not asked in the Name of the Saviour"

From the Holy Gospel according to John
John 16:23-3
At that time, Jesus said unto His disciples: Amen, Amen, I say unto you: Whatsoever ye shall ask the Father in My Name, He will give it you. And so on.

Homily by St. Augustine, Bishop of Hippo.
102nd Tract on John.
We have now to consider these words of the Lord "Amen, Amen, I say unto you, Whatsoever ye shall ask the Father in My Name, He will give it you." It hath already been said in the earlier part of this discourse of the Lord, for the sake of some who ask the Father in Christ's Name and receive not, that whatsoever is asked, which tendeth not to salvation, is not asked in the Name of the Saviour. By the words "In My Name" we must not understand the vocalization of letters and syllables, but the meaning of what is said, the honest and true meaning.